1. Field of the Invention
This invention relates to lockable differentials that can be locked into a non-differentialing mode. More specifically this invention is concerned with the automatic control necessary to lock a differential without direct operator action.
2. Description of the Prior Art
In heavy equipment vehicles such as used in the construction and earth-moving industry a lockable differential may be incorporated in the drive train of the vehicle. For instance, a scraper which has a forward portion with an engine and drive train as well as a rearward portion having an engine and drive train may incorporate a lockable differential in the forward portion drive train as well as in the rear portion drive train. In a scraper have only a single engine and drive train only one lockable differential would be used. The lockable differential would be activated by the scraper operator through manipulation of a differential locking control at times when the scraper requires more traction than is delivered with a traction responsive differential.
The locking function desired in the lockable differential herein described is concerned with straight line vehicle movement when it is highly advantageous to have both left and right drive wheels rotating at identical speeds without the slip of either.
The lockable differential under consideration in this application is of the type incorporating a clutch pack mounted between the spider assembly and the ring gear of a conventional differential. The clutch pack is air operated responsive to a switch under control of the vehicle operator. It should be noted that the lockable differential will perform exactly as a conventional differential until a control switch is closed manually as with contemporary systems or automatically as with the system disclosed in this invention.
The present method of operating an air lock type of lockable differential of self-loading elevator type scrapers is to have the operator operate an on-off foot valve. This valve is normally closed and is spring loaded to the closed or "off" position. In some instances of scraper operation the operators are not actuating the power train air lock differential when loading or unloading and the different gears are being damaged due to excessive wheel slippage.
The invention disclosed herein results from the need of having a lockable differential capable of being locked without cognitive action on the part of the operator. In the scraper example it would be beneficial to have the lockable differential lock up when the scraper is being loaded and the bowl is lowered to bite into the ground or when the bowl is lowered to dispense the load. As the operator has other vehicle controls to attend to during this time it is advantageous to relieve him of the duty to manually lock the differential. This is accomplished in the instant invention by having a lockable differential control switch responsive to the status of sundry or peripheral equipment of the vehicle.
There are numerous other types of vehicles and equipment that use differentials than can also benefit from the invention set forth herein. For instance, loaders, dozers, graders, dump trucks, highway trucks as well as stationary equipment using differentials may be contemplated to advantageously use the differential control of this invention.